Quasi-Isotropic Triaxially Braided Cellulose-Reinforced Composites

In this article, we investigate experimentally and analytically the mechanical properties of a natural fiber quasi-isotropic triaxially braided composite. The composite is prepared from triaxially braided regenerated cellulose fibers and a high-bio-content epoxy resin system using a resin infusion process. Simultaneous mechanical loading, digital image correlation, and acoustic emission tests were performed on notched and unnotched specimens to understand the tensile behavior of the composites and the initiation and propagation of damage. Experimental results were compared with the effective tensile properties determined using an analytical model. The model is a discrete three-layer analytical representation based on a mechanics transformation-based representation of the quasi-isotropic braided layers. The model is used to determine the elastic stiffness and Poisson effects based on the constituent properties such as the fiber volume fractions, the waviness of the bias tows, and the relative thickness of the braided preform. The experimental results show the analytical model's ability in predicting the composite's elastic properties. The unique fabric architecture is found to have a large influence on the strength properties across the different specimen geometries investigated.